Detachable sprocket drive for a mill drum with inside liner

ABSTRACT

A chain and sprocket drive for a mill drum in which a plurality of abutting tooth-carrying members, each having radially projecting teeth, are affixed to the outer surface of the drum to form a sprocket thereon driven by the chain.

Graham Apr. 9, 1974 DETACI-IABLE SPROCKET DRIVE FOR A MILL DRUM WITH INSIDE LINER [75] Inventor: Richard B. Graham, Columbus,

Ohio I [73] Assignee: Jeffrey Galion Inc., Columbus, Ohio [22] Filed: Sept. 11, 1972 [21] Appl. No.: 287,884

[52] US. Cl 74/243 DR, 74/243 R [51] Int. Cl. F16h 55/30 [58] Field of Search 74/243, 243 DR [56] References Cited UNITED STATES PATENTS 1,423,028 7/1922 Roth 74/243 R 1,638,140 8/1927 Best 74/243 R 3,311,220 3/1967 IAnson 74/243 R 1,736,758 11/1929 Ball 74/243 R 3,446,089 5/1969 Stockton 74/243 R FOREIGN PATENTS OR APPLICATIONS 675,693 12/1963 Canada 74/243 R OTHER PUBLICATIONS Primary Examiner- -Leonard H. Gerin Assistant Examiner-Allan Russell Burke Attorney, Agent, or Firm-David Young [57] ABSTRACT A chain and sprocket drive fora mill drum in which a plurality of abutting tooth-carrying members, each having radially projecting teeth, are affixed to the outer surface of the drum to form a sprocket thereon driven by the chain.

12 Claims, 6 Drawing Figures BACKGROUND OF THE INVENTION 1. Field of the Invention The instant invention relates to a chain and sprocket drive for a mill drum in which a plurality of toothcarrying members are secured to the outer surface of the drum to form a sprocket thereon driven by the chain.

2. Description of the Prior Art The largest autogeneous iron ore grinding mills presently existing or being constructed are 32 feet in diameter and use approximately 6,000 horsepower. A common drive system for these mills has an electric motor driving a reduction unit which has a pinion that drives a bull gear on the shaft on which a mill drum is mounted. Such a drive is satisfactory in smaller mills and in the existing large mills. However, the teeth on the gears used in the large existing mills are highly stressed when transmitting 4,000 horsepower and it presently appears that 6,000 horsepower is the practical limit of the amount of power which can be transmitted through a single gear and pinion set. It is possible to use a plurality of pinions to drive a common bull gear to transmit power from several prime movers to a large grinding mill drum. However, multiple driving pinions are expensive and require close manufacturing tolerances and allowances. Furthermore, it is very difficult to maintain an equal distribution of the drum load among several driving pinions when rotation of a grinding mill drum is being started from rest. It is desirable to find a drive system for grinding mills which is suitable for driving mill drums which are larger and require much more power than the existing mill drums. Furthermore, such a drive system should be less complex to manufacture than a drive system using multiple pinions to drive a common bull gear.

SUMMARY The instant invention provides a chain and sprocket drive for a grinding mill drum. A plurality of toothcarrying members are affixed to the outer surface of the mill drum to form a sprocket thereon. Adjacent tooth-carrying members abut each other and each tooth-carrying member has radially projecting teeth. The sprocket formed on the mill drum by the teeth on the tooth-carrying members is driven by a drive chain.

The instant chain and sprocket drive is suitable for transmitting the required power to different sizes of mill drums, including very large drums. The amount of power that can be transmitted by the instant drive is simply a function of the number of teeth on the toothcarrying members and the number of rows of toothcarrying members positioned on the outer surface of a mill drum which form sprockets adpated to be driven by drive chains. The members forming a sprocket can be any desired size and are easily manufactured. The chain in the instant chain drive will accept both out-ofround and concentricity errors of a sprocket formed on a drum to a fairly large degree, particularly if the sprocket is large. Therefore, the drum. and sprocket components in the instant chain and sprocketdrive do not require unusually close. manufacturing tolerancesand allowances.

It is an object of the instant invention to provide a chain and sprocket drive for a mill drum in which aplurality of abutting tooth-carrying members are secured to the outer surface of a drum to form a sprocket adapted to be driven by a drive chain.

It is another object of the instant invention to provide a chain and sprocket drive for a mill drum in which a plurality of abutting tooth-carrying members are secured to the outer surface of the drum to form a sprocket driven by a drive chain, a plurality of liner plates are affixed to the inner surface of the drum, and either of said tooth-carrying members or said liner plates can be removed from said drum independently from the other.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims. A

DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of a grinding mill drum incorporating the chain and sprocket drive of this invention.

FIG. 2 is a plan view of a tooth-carrying member of this invention.

FIG. 3 is a plan view of a portion of a mill drum incorporating the chain and sprocket drive of this invention.

FIG. 4 is a sectional view on the line 44 of FIG. 3.

FIG. 5 is a view partially in section on the line 5-5 of FIG. 3.

FIG. 6 is a view ofa portion of FIG. 5 showing the direction in which forces are transmitted in the chain and sprocket drive of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT A cylindrical grinding mill drum l0 whichis rotatable about a horizontal axis is shown in FIG. 1. A drive sprocket 14 is rotatably mounted about an axis parallel to that of the mill 'drum 10. Force is transmitted from the drive sprocket 14 to a sprocket 18 formed on the mill drum 10 by a drive chain 20 causing the latter sprocket l8 and the drum 10 to rotate. .The driven sprocket 18 has a plurality of abutting tooth-carrying members 22 secured to the outer surface of the mill drum 10.

Each tooth-carrying member 22 has a plurality of laterally spaced teeth 32 as seen in FIG. 2. The teeth 32 are centered between the ends 34 of the member 22. Each tooth-carrying member 22 is an identical casting and any number of teeth 32 can be formed thereon.

Feet 36 are spaced along the ends 34 0f each toothcarrying member 22. The feet 36 project downwardly from the member 22 and engage the outer surface 24 of the drum l0. Semi-circular openings 38 are spaced along the ends 34 above the feet 36. A smaller semicircular opening 40 extends downwardly through each foot 36 from within each of the larger openings 38. Integral flanges 37 which engage the outer surface 24 of the drum 10 are formed on the corners of each toothouter surface 24 of the drum 10. Each of the ends 34 of a member 22 abut an end 34 of an adjacent member 22. The semi-circular openings 38 spaced along the ends 34 of a pair of abutting tooth-carrying members 22 are aligned to form circular openings as can be'seen in FIG. 3. The semi-circular openings 40 within each larger opening 38 along the ends 34 of a pair of abutting tooth-carrying members 22 are aligned to form apertures extending downwardly through the feet 36 of the abutting pair of members 22 as seen in FIGS. 4 and 5.

A plurality of liner plates 26 are attached to the inner surface 28 or the drum 10. The liner plates 26 prevent the inner surface 28 from contacting and being abraded by material which is processed in the drum 10. The processed material abrades the liner plates 26 which can be removed from the drum l and replaced when necessary.

Each tooth-carrying member 22 is secured to the outer surface 24 of thedrurn by a plurality of loadcarrying bolts 44 which transmit force from the member 22 to the drum 10. Each bolt 44 passes through an aperture 48 in the drum 10 and through an aperture formed by a complementary pair of walls in the semicircular openings 40 adjacent the ends 34 of two abutting members 22 to engage a nut 46 and rigidly secure a pair of members 22 to the outer surface 24. Each nut 46 is positioned in an aperature formed by a complementary pair of walls in the semi-circular openings 38. Thus each bolt 44 is positioned midway between the teeth 32 of the pair of members 22 it engages. The load-carrying bolts 44 which secure the tooth-carrying members 22 to the outer surface 24 of the drum 10 also retain the liner plates 26 in contact with the inner surface 28 of the drum as seen in FIGS. 4 and 5. Each of the bolts 44 has a portion of its shank which is square. The square portion 50 of each bolt 44 passes through a close fitting square aperture 52 cast in a liner plate 26. Consequently, the bolts 44 are prevented from rotating when nuts 46 are turned thereon. The heads of the bolts 44 are in countersinks in the liner plates 26 to prevent their being damaged by the material processed in the drum l0.

A plurality of threaded studs 54 are fastened to the drum l0 and project upwardly through the apertures 42 formed in the flanges 37 at the corners of each tooth-carrying member 22. A nut 56 engages each stud 54. The studs 54 and nuts 56 provide an additional means for retaining the tooth-carrying members 22 on the drum 10. The studs 54 do not transmit force from the "tooth-carrying members 22 to the drum 10 but merely retain the tooth-carrying members 22 on the outer surface 24 when the load-carrying bolts 44 are removed. These bolts 44 are necessarily removed when the liner plates 26 are replaced.

The liner plates 26 are positioned on the inner surface 28 of the drum 10 in .such a way that each liner plate 26 is secured by bolts 44 which retain several pairs of tooth-carrying members 22. Therefore, if some of the bolts 44 are removed to permit the removal of a tooth-carrying member 22, none of the liner plates 26 is disturbed since each is still retained by bolts 44 which engage remaining members 22. Any of the bolts 44 which engage the tooth-carrying members 22 and the liner plates 26 can be removed to permit the removal of the liner plates 26 without disturbing the toothcarrying members 22. This is because the members 22 are also retained on the drum 10 by means of the studs 54 and nuts 56. If a tooth-carrying member 22 is to be removed from the outer surface 24 of the drum 10, the bolts 44 which engage the tooth-carrying member 22 and also the nuts 56 on the studs 54 which pass through the member 22 must be removed.

The teeth 32 on each tooth-carrying member 22 are laterally spaced from each other along a line parallel to the axis of the mill drum 10. When the tooth-carrying members 22 are positioned on the outer surface 24 of the drum 10 to form a sprocket 18, the teeth 32 are arranged in a plurality of circumferential rows 60, 62 and 64, as seen in FIG. 3. The rows 60, 62 and 64 form a multiple sprocket 18 having radially projecting teeth on the outer surface 24 of the drum 10. The bolts 44 and nuts 46 which secure the tooth-carrying members 22 to the drum 10 are positioned within these rows.

The multiple sprocket 18 is engaged by a drive chain 20 which has a number of strands equal to the number' of rows of teeth 60, 62 and 64 on the sprocket 18. The drive chain 20 is comprised of a plurality of links 66. Each link 66 has a bushing 68 positioned between a pair of idential offset'sidebars 70. The bushing 68 is press fitted into apertures in each of the two sidebars 70 to prevent relative movement therebetween. The links 66 are joined together to form the multiple strand drive chain 20 by chain pins 72. The chain pins 72 pass through the sidebars 70 and bores 74 in the bushings 68 of the chain links 66. The chain pins 72 are rigidly affixed to keepers 76 which are welded to the outer sidebars 70 of the links 66 in the outer tooth rows 60 and 64 as seen in FIGS. 3 and 5. The keepers 76 prevent the chain pins 72 and sidebars 70 from rotating relatively to each other.

The distance between the teeth 32 on adjacent toothcarrying members 22 in the same row 60, 62 or 64 of the sprocket 18 is two chain pitches as can be seen in FIGS. 3 and 5. Such a spacing between the teeth 32 permits access to the bolts 44 and nuts 46 between pairs of bushings 68 in a row of the drive chain 20 which do not receive a tooth 32. Therefore, the bolts 44 can be removed from the drum 10 to permit the removal of the liner plates 26 without removing the drive chain 20 from the sprocket 18 on the drum 10.

The drive sprocket 14 transmits force, for rotating the driven sprocket l8 and the drum 10 to which the sprocket 18 is rigidly-affixed, through the drive chain 20. Bushings 68 on the chain 20 contact the sprocket teeth 32 and transmit force to the tooth-carrying members 22 forming the sprocket 18. The tooth force is directed along a line 80 that forms the angle 0 with the line 82 through the axes of the chain pins 72,72. The angle 6 is generally referred to as the pressure angle, and in the force system of this chain and sprocket drive, the pressure angle 0 must be such that the line 80 of the force is directed through and intersects the shear plane of the load-carrying bolts 44. The shear plane is coincident with the outer surface 24 of the drum 10 and extends through the bolts 44. The force acting along the line 80 through a tooth-carrying member 22 is resisted by the bolts 44 and loads the bolts 44 in shearv Any force not resisted by the bolts 44 is transmitted to an abutting tooth-carrying member 22. The tooth-carrying members 22 of the sprocket 18 firmly abut each other along their ends 34 and when the load-carrying bolts 44 are tightened the members 22 form a substantially rigid cylinder. This cylinder tends to resist crushing of the drum 10, since any force not taken by the bolts 44 is transmitted to an abutting member 22 and is not concentrated in the area of the bolts 44 as would happen if the members 22 were not firmly abutting each other.

The ability of the rigid cylinder to resist crushing of the drum is not impaired if the pressure angle is slightly reduced as the tooth force would be transmitted along a line above the shear plane of the bolts 44 and passing through an adjacent tooth-carrying member. Consequently, any portion of the tooth force tending to shear the bolts 44 and not taken by the bolts 44 would still be transmitted to the adjacent member. However, reducing the pressure angle 0 is not desirable for the reason that the tooth force would be acting to pivot the member 22 about the portion of its edge 34 which is in the shear plane of the bolts 44 and consequently thebolts 44 at the opposite edge 34 are placed in tension to resist the pivoting tendency.

Increasing the pressure angle 0 is particularly undesirable as the tooth force is transmitted along a line which acts to push the tooth-carrying member 22, through which it passes, inwardly and tends to crush the drum. Since the tooth force is not directed toward an abutting member 22, the advantage of a cylinder formed by the abutting members 22 to prevent the drum from being crushed, is lost. Consequently, it is preferred that the pressure angle 0 be such that the tooth force passes through the shear plane of the bolts.

Any number of teeth 32 can be formed on the individual tooth-carrying members 22 to form a multiple sprocket 18. Each sprocket 18 would be driven by a drive chain 20 having a number of strands equal to the number of rows of teeth formed on the sprocket 18. It is contemplated that for large mill drums requiring a large amount of power a plurality of parallel rows of tooth-carrying members may be arranged on the outer surface of a mill drum to form a plurality of multiple sprockets. Such an arrangement would provide a relatively uniform distribution of the driving force exerted on the sprockets by the chains across theouter surface of the drum parallel to its axis and would reduce the possibility of crushing the drum.

The chain and sprocket drive of the instant invention provides a drive for large drums which is relatively easy to manufacture and does not require extremely close manufacturing tolerances and allowances. Further, the instant chain and sprocket drive is suitable for driving larger mill drums than are presently being constructed.

Obviously, those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims hereto appended, and applicant, therefore, wishes not to be restricted to the precise construction herein disclosed.

Having thus described and shown an embodiment of the invention, what is desired to secure by Letters Patent of the United States is:

1. A chain and sprocket drive for a drum comprising, a drum, a drive sprocket, a driven sprocket on the outer surface of said drum, a chain engaged with said drive sprocket and said driven sprocket for transmitting force from said drive sprocket to said driven sprocket to rotate said drum, said driven sprocket having a plurality of tooth members, a radially projecting tooth on each of said tooth members, said tooth members being circumferentially positioned on said outer surface, said outer surface of said drum being substantially cylindrical, fastening means engaging said tooth members and to secure the members on said cylindrical surface, said tooth members each having surfaces in abutting relation to adjacent members, said fastening means extending through said tooth members and through said drum to receive the load of the drive from said chain, said teeth on said tooth members form a circumferential row of teeth engaged by said chain, and a second fastening means engaging each of said tooth members to retain said tooth members on the drum surface when the first said fastening means is removed.

2. A chain and sprocket drive for a drum as recited in claim 1, wherein said fastening means extends radially, and each of said fastening means engages two adjacent tooth members.

3. A chain and sprocket drive for a drum as recited in claim 1, wherein each of said tooth members has two of said abutting surfaces, said adjacent tooth members have complementary walls defining apertures at said abutting surfaces for receiving said fastening means, and said fastening means comprises load-carrying bolts extending through said apertures and said drum.

4. A chain and sprocket drive for a drum as recited in claim 1, wherein alternate chain links of said chain engage said teeth on said tooth members, and said teeth are spaced from each other by a distance of two chain pitches.

5. A chain and sprocket drive for a drum as recited in claim 4, wherein said fastening .means comprises load-carrying bolts each spaced an equal distance from a tooth on each of two adjacent tooth members engaged by a load carrying bolt, and said load carrying bolts are accessible through alternate chain links of said chain which do not receive a tooth.

6. A chain and sprocket drive for a drum comprising, a drum, a drive sprocket, a driven sprocket on the outer surface of said drum, a chain engaged with said drive sprocket and said driven sprocket for transmitting force from said drive sprocket to said driven sprocket to rotate said drum, said driven sprocket having a plurality of tooth members, a radially projecting tooth on each of said tooth members, a plurality of liner plates in abutting disposition on the inner surface of said drum, said tooth members being circumferentially positioned on said outer surface, said outer surface of said drum being substantially cylindrical, fastening means which engage said tooth members and secure the members on said cylindrical surface, said fastening means extending through said tooth members and said drum and engaging said liner plates to retain them in abutting contact with said inner surface of said drum, and said teeth on said tooth members form a circumferential row of teeth engaged by said chain.

7. A chain and sprocket drive for a drum as recited in claim 6, wherein said fastening means includes a plurality of load-carrying bolts that engage the drum to transmit the force of the drive.

8. A chain and sprocket drive for a drum as recited in claim 7, wherein each of said load-carrying bolts extends through a liner plate and engages a pair of tooth members, and each liner plate is secured by at least a plurality of load-carrying bolts which engage at least three tooth members such that the load carrying bolts securing any one of the tooth members can be removed to permit a tooth member to be removed and each of said liner plates will be retained in contact with the inner surface of said drum by load-carrying bolts which pass through remaining tooth members.

9. A chain and sprocket drive for a drum as recited in claim 7 including a second fastening means which engages each of said tooth members to retain said tooth members on said outer drum surface when said loadcarrying bolts are removed.

10. A chain and sprocket drive for a drum comprising, a drum, 3 drive sprocket, a driven sprocket on the outer surface of said drum, a chain engaged with said drive sprocket and said driven sprocket for transmitting force from said drive sprocket to said driven sprocket to rotate said drum, said driven sprocket having a plurality of tooth members, said outer surface of said drum being substantially cylindrical, fastening means which pass through said drum, adjacent tooth members having surfaces which firmly abut each other such that said tooth members form a substantially rigid sprocket which resists crushing of said drum, each of said fastening means engages a pair of adjacent members at their abutting surfaces, and said force of said drive sprocket is transmitted by said chain to said driven sprocket and is applied to a tooth of a tooth member along a line of force that extends through said fastening means in a plane between said tooth member and the outer surface of the drum.

1 l. A chain and sprocket drive for a drum as recited in claim 10, wherein said fastening means includes a plurality of load-carrying bolts, said force transmitted from said chain to said driven sprocket to rotate said drum passes through said tooth members and is applied to said bolts to load them in shear.

12. A chain and sprocket drive as recited in claim 1 1, wherein the line of force passing through each of said toot-h members is directed through and intersects said shear plane of said load-carrying bolts. 

1. A chain and sprocket drive for a drum comprising, a drum, a drive sprocket, a driven sprocket on the outer surface of said drum, a chain engaged with said drive sprocket and said driven sprocket for transmitting force from said drive sprocket to said driven sprocket to rotate said drum, said driven sprocket having a plurality of tooth members, a radially projecting tooth on each of said tooth members, said tooth members being circumferentially positioned on said outer surface, said outer surface of said drum being substantially cylindrical, fastening means engaging said tooth members and to secure the members on said cylindrical surface, said tooth members each having surfaces in abutting relation to adjacent members, said fastening means extending through said tooth members and through said drum to receive the load of the drive from said chain, said teeth on said tooth members form a circumferential row of teeth engaged by said chain, and a second fastening means engaging each of said tooth members to retain said tooth members on the drum surface when the first said fastening means is removed.
 2. A chain and sprocket drive for a drum as recited in claim 1, wherein said fastening means extends radially, and each of said fastening means engages two adjacent tooth members.
 3. A chain and sprocket drive for a drum as recited in claim 1, wherein each of said tooth members has two of said abutting surfaces, said adjacent tooth members have complementary walls defining apertures at said abutting surfaces for receiving said fastening means, and said fastening means comprises load-carrying bolts extending through said apertures and said drum.
 4. A chain and sprocket drive for a drum as recited in claim 1, wherein alternate chain links of said chain engage said teeth on said tooth members, and said teeth are spaced from each other by a distance of two chain pitches.
 5. A chain and sprocket drive for a drum as recited in claim 4, wherein said fastening means comprises load-carrying bolts each spaced an equal distance from a tooth on each of two adjacent tooth members engaged by a load carrying bolt, and said load carrying bolts are accessible through alternate chain links of said chain which do not receive a tooth.
 6. A chain and sprocket drive for a drum comprising, a drum, a drive sprocket, a driven sprocket on the outer surface of said drum, a chain engaged with said drive sprocket and said driven sprocket for transmitting force from said drive sprocket to said driven sprocket to rotate said drum, said driven sprocket having a plurality of tooth members, a radially projecting tooth on each of said tooth members, a plurality of liner plates in abutting disposition on the inner surface of said drum, said tooth members being circumferentially positioned on said outer surface, said outer surface of said drum being substantially cylindrical, fastening means Which engage said tooth members and secure the members on said cylindrical surface, said fastening means extending through said tooth members and said drum and engaging said liner plates to retain them in abutting contact with said inner surface of said drum, and said teeth on said tooth members form a circumferential row of teeth engaged by said chain.
 7. A chain and sprocket drive for a drum as recited in claim 6, wherein said fastening means includes a plurality of load-carrying bolts that engage the drum to transmit the force of the drive.
 8. A chain and sprocket drive for a drum as recited in claim 7, wherein each of said load-carrying bolts extends through a liner plate and engages a pair of tooth members, and each liner plate is secured by at least a plurality of load-carrying bolts which engage at least three tooth members such that the load carrying bolts securing any one of the tooth members can be removed to permit a tooth member to be removed and each of said liner plates will be retained in contact with the inner surface of said drum by load-carrying bolts which pass through remaining tooth members.
 9. A chain and sprocket drive for a drum as recited in claim 7 including a second fastening means which engages each of said tooth members to retain said tooth members on said outer drum surface when said load-carrying bolts are removed.
 10. A chain and sprocket drive for a drum comprising, a drum, a drive sprocket, a driven sprocket on the outer surface of said drum, a chain engaged with said drive sprocket and said driven sprocket for transmitting force from said drive sprocket to said driven sprocket to rotate said drum, said driven sprocket having a plurality of tooth members, said outer surface of said drum being substantially cylindrical, fastening means which pass through said drum, adjacent tooth members having surfaces which firmly abut each other such that said tooth members form a substantially rigid sprocket which resists crushing of said drum, each of said fastening means engages a pair of adjacent members at their abutting surfaces, and said force of said drive sprocket is transmitted by said chain to said driven sprocket and is applied to a tooth of a tooth member along a line of force that extends through said fastening means in a plane between said tooth member and the outer surface of the drum.
 11. A chain and sprocket drive for a drum as recited in claim 10, wherein said fastening means includes a plurality of load-carrying bolts, said force transmitted from said chain to said driven sprocket to rotate said drum passes through said tooth members and is applied to said bolts to load them in shear.
 12. A chain and sprocket drive as recited in claim 11, wherein the line of force passing through each of said tooth members is directed through and intersects said shear plane of said load-carrying bolts. 